The present invention relates to compositions for making closures and closure liners, and more particularly to compositions that are free of erucamide.
It is known to make container closures and closure sealants using polymers with erucamide as a slip agent. However, erucamides are ethylenically-unsaturated amides that react with ozone that is used for sterilization, thereby creating aldehyde off-tastes that adversely affect beverage products such as carbonated water and soft drinks. However, the use of saturated amides, such as behenamide, while avoiding the off-taste problem, tend to be less effective as slip aids because it is believed that they migrate more slowly to the surface of the matrix polymer and thereby are less efficacious in providing a low-friction surface.
As noted in World Patent WO 0236672A1 of Alphagary Corporation, it was noted that conventional closure sealants for beverage or food containers have utilized lubricants such as erucamide and oleamide, each of which is conjugated. Because these lubricants are conjugated, they are susceptible to photochemical breakdown and oxidative breakdown. In other words, oxidative breakdown of erucamide by ozone sterilization can create flavor-detracting contaminants such as ketones in addition to aldehydes. Ozone sterilization is frequently performed to sterilize bottled water products, such as mineral water and spring water. The United States Food and Drug Administration requires ozone sterilization for sterilizing bottled water products manufactured and sold in the United States. Thus, there is a need for a closure sealant lubricant that is resistant to oxidative breakdown from ozone sterilization. Additionally, there is a need for a closure sealant lubricant that is resistant to photochemiclal breakdown.
Thus, a novel erucamide-free composition is needed for making container closures and closure sealants.
In surmounting the problems noted above, the present invention provides a composition, suitable for container closures and closure sealants, comprising: (A) a matrix polymer, copolymer, or blend of polymer and/or copolymers, which is essentially free of erucamide and which is essentially free of unsaturated amide; (B) a silicone lubricant having an average molecular weight not less than 40,000 and being present in an amount not less than 0.01 parts and not greater than 10 parts based on 100 parts of the base polymer(s); and (C) a slip aid comprising a saturated amide, an oxidized polyethylene, or mixture thereof; the slip aid being in an amount not less than 0.01 parts and not greater than 8 parts based on 100 parts of the base polymers(s).
Polymers, copolymers, and blends thereof which are conventionally known for use as matrix polymers for closures and sealants are contemplated for use in the present invention.
The present invention is also directed to a lubricant/slip-aid composition for use in container closures and closure sealants. An exemplary slip aid composition comprises: a silicone lubricant (e.g., siloxane, organosiloxane) having an average molecular weight greater than 40000, the silicone being present in an amount of 0.01 partsxe2x80x9410 parts based on 100 parts of matrix polymer(s) and a slip aid comprising a saturated amide, an oxidized polyethylene, or mixture thereof.
Further advantages and features are described in further detailed hereinafter.